A tablet display is promoted in recent years due to its characteristics such as ultra-thin thickness and energy-saving. Shift registers are used in most tablet displays, wherein the shift registers are implemented by a method for integrating a gate driving apparatus on a liquid crystal panel (gate on array, GOA), thus omitting a gate driving Integrated Circuit (IC) and reducing a manufacturing process, so that not only the cost for manufacturing the tablet display is decreased, but also the period for manufacturing the tablet display is shorten to some extent. Therefore, the technique of GOA is widely used in manufacturing of the tablet display in recent years. However, there is a problem existed that the output stability of GOA is to be addressed in the design of GOA.
FIG. 1 shows a basic unit of GOA in prior art, wherein the basic unit of GOA comprises six Thin Film Transistors (TFTs) M12, M19, M20, M21, M22, M23 and a capacitor C1, and CLK, CLKB represent clock signals, VGH represents a positive power supply voltage, VGL represents a negative power supply voltage, STV represents an input signal, and a node B represents a pull-down node; in an actual application, a node A and a node C in the GOA interfere with each other due to a residual voltage signal of a previous period, affecting the turning-on of TFT M19, and the shift register can not operate stably for a long time, so that the output signal of the output terminal OUTPUT is unstable.